1. Field of the Invention
The present invention relates to an adaptive multiplexing/demultiplexing method, and a multiplexer/demultiplexer using the same in the H.324M system, and more particularly, to an adaptive multiplexing/demultiplexing method capable of being effectively used in an error-prone channel, and a multiplexer/demultiplexer using the method.
2. Description of the Related Art
In general, the H.324M recommendation prescribes a multiplexing of video and audio signals which is effective in an error-prone channel such as a wireless channel, and includes H.223 multiplexing, H.223/Annex C multiplexing, H.245 controlling, a H.263 video coder/decoder (CODEC) and a G.723.1 audio CODEC. Particularly, according to the H.223 recommendation, in order to achieve video telephone and video conferencing in a general digital telecommunication network by the ITU-T (the Telecommunication standardization sector of the International Telecommunication Union), video, audio and other data are adaptively multiplexed in protocol data units (PDU) and then later demultiplexed. An H.223 multiplexer/demultiplexer (MUX/DEMUX) can be used when a channel bit error rate is 10xe2x88x926 or less. An H.223/Annex C MUX/DEMUX is a new MUX/DEMUX capable of improving error robustness, obtained by adding rate compatible punctured convolutional coder/decoder (RCPC CODEC) and automatic retransmission on request (ARQ) functions to the H.223 MUX/DEMUX. According to the H.223/Annex C MUX/DEMUX, when an error occurs in a receiver, the RCPC-encoded data is retransmitted by a transmitter at different rates.
However, it is nearly impossible to use the H.223 MUX/DEMUX in an error-prone channel due to its low error-resiliency. Also, in the case of the H.223/Annex C MUX/DEMUX, channel throughput is steeply decreased due to the ARQ, and there is extremely high complexity due to the RCPC. A measure of complexity can be determined by the amount or type of error protection components included in a multiplexing/demultiplexing scheme, for example.
To solve the above problems, it is an object of the present invention to provide an adaptive multiplexing/ demultiplexing method and a multiplexer/demultiplexer (MUX/DEMUX) using the same, in which a plurality of MUX/DEMUXs having different complexities are defined between the H.223 MUX/DEMUX and the H.223/Annex C MUX/DEMUX, so that the multiplexing can be achieved selectively according to specific circumstances by selecting between the plurality of MUX/DEMUXs, to match a particular circumstance via a trade-off of overhead of the MUX/DEMUXs.
According to an aspect of the object, there is provided an adaptive multiplexing/demultiplexing method in an H.324M system, the method comprising the steps of: (a) performing a first multiplexing/demultiplexing process having at least one of: the complexity and performance of the H.223 recommendation; (b) performing a second multiplexing/demultiplexing process having at least one of: the complexity of the H.223/Annex C recommendation; and (c) inserting one or more of a third type of multiplexing/demultiplexing processing having at least one of different complexities and performance levels from the steps (a) and (b)
Preferably, the third multiplexing/demultiplexing process of the step (c) uses a high-level data link control (HDLC) flag including an extra pseudo-random noise (PN) code having more bits than the H.223 recommendation.
Preferably, the third multiplexing/demultiplexing process of the step (c) comprises the substeps of: (c1) using an HDLC flag including an extra PN code having more bits than the H.223 recommendation; and (c2) using a header having more bits than the H.223 recommendation.
Preferably, the third multiplexing/demultiplexing process of the step (c) comprises the substeps of: (c1) using an HDLC flag including an extra PN code having more bits than the H.223 recommendation; (c2) using a header having more bits than the H.223 recommendation; and (c3) using error protection bits in either an adaptation layer or a multiplexer layer.
According to another aspect of the object, there is provided an adaptive multiplexer/demultiplexer (MUX/DEMUX) in an H.324M system, comprising: an H.223 MUX/DEMUX; an H.223/Annex C MUX/DEMUX; and one or more intermediate MUX/DEMUXs between the H.223/Annex C MUX/DEMUX and the H.223 MUX/DEMUX, having different complexities to the H.223/Annex C MUX/DEMUX and the H.223 MUX/DEMUX.
Preferably, the one or more intermediate MUX/DEMUXs uses a high-level data link control (HDLC) flag including an extra pseudo-random noise (PN) code having more bits than the H.223 recommendation.
Preferably, the one or more intermediate MUX/DEMUXs uses an HDLC flag including an extra PN code having more bits than the H.223 recommendation, and a header-having more bits than the H.223 recommendation.
Preferably, the one or more intermediate MUX/DEMUXs uses an HDLC flag including an extra PN code having more bits than the H.223 recommendation, a header having more bits than the H.223 recommendation, and error protection bits in either an adaptation layer or a multiplex layer.